Compressor Voltage Cutoff Control for Ultralow Freezer Protection
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Solution Overview
Problem
In refrigerating apparatuses, particularly ultracold freezers, compressor locking due to overheating or voltage fluctuations can lead to overcurrents, causing damage to biotic samples and potentially welding bimetal protection circuits, resulting in repeated circuit breaker operations and loss of cooling capacity.
Innovation Solution
A control apparatus that includes a voltage measuring unit and a control unit to trip a second circuit breaker before an overcurrent occurs when the power supply voltage drops, ensuring the compressor current is interrupted and resumed only when the voltage recovers, thereby preventing compressor damage and maintaining cooling capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a manual-reset-type circuit breaker is used to protect against compressor locking, then the system is protected from overcurrent damage, but the freezing circuit remains at rest after voltage recovery requiring manual reset operation
Solution Approach 1:
The circuit breaker is designed to automatically detect voltage recovery and reset itself without requiring manual intervention. The control unit monitors power supply voltage and automatically closes the circuit breaker when voltage returns to normal levels, enabling the system to serve itself during recovery from voltage drops.
Solution Approach 2:
The control unit continuously monitors the power supply voltage and uses this feedback information to determine when to trip or reset the circuit breaker. When voltage drops below a threshold, the breaker is tripped; when voltage recovers above the threshold, the breaker is automatically reset, creating a closed-loop control system.
2Reliability
If the circuit breaker is set to operate before the main circuit breaker, then the individual freezing circuit is protected, but repeated operations may cause welding of the bimetal protection circuit
Solution Approach 1:
The patent replaces the mechanical bimetal protection circuit with an electronic control system. The control unit monitors voltage and current conditions electronically and controls the circuit breaker operation, eliminating the mechanical bimetal component that is susceptible to welding from repeated operations.
Solution Approach 2:
The control unit detects voltage drops before they cause compressor locking and trips the circuit breaker in advance. By taking preliminary action to prevent the abnormal condition from developing, the system avoids the repeated tripping and resetting that would lead to bimetal welding.
3Productivity
If the compressor is allowed to operate during voltage drop, then cooling capacity is maintained, but overcurrent flows causing compressor damage
Solution Approach 1:
The control unit monitors power supply voltage and compares it against predetermined thresholds. When voltage drops below the threshold, the system changes the operational parameter by tripping the circuit breaker to stop compressor operation, preventing overcurrent damage while maintaining safety.
Data Source
AI summary
A control apparatus, which controls a refrigerating apparatus including a compressor and a first circuit breaker that interrupts a current flowing through the compressor when the current, flowing from a power supply through the compressor to cause the compressor to work, becomes greater than a predetermined current and that is closed according to an operation by a user, includes: a voltage-measuring unit to measure a power-supply voltage a control unit to trip a second circuit breaker disposed in series with the first circuit breaker so that the current from the power supply flowing through the compressor is interrupted, when the measured power-supply voltage becomes lower than a predetermined voltage, and close the second circuit breaker after the power-supply voltage becomes higher than the predetermined voltage, the predetermined current corresponding to a current greater than the current flowing through the compressor when the power-supply voltage is equal to the predetermined voltage.